The name originated from the tradition of starting X11 program names with X, but nowadays is read as "eXtremely evil" or any number of obvious derivatives of this. It is currently licensed under the GPL.

From the documentation: You sinned in life. And now you must pay. Satan pits the recently deceased against each other to fight for rank in Hell. Your skill determines your fate for all eternity. This contest is known as XEvil.

There are many different player types, each with different abilities: eg the Ninja who can hang onto walls and ceilings and the Chopper Boy who can fly.